How do we know that the neurons of an artificial neural network start by learning small features?
We do it experimentally; you're able to look at what each layer is learning by tweaking various values throughout the network and doing gradient ascent. For more detail, watch this lecture: https://www.youtube.com/watch?v=6wcs6szJWMY&amp;list=PL3FW7Lu3i5JvHM8ljYj-zLfQRF3EO8sYv&amp;index=12 it provides many methods used for understanding exactly what your model is doing at a certain layer, and what features it has learnt.